Low temperature preparation of tungsten nanoparticles from molten salt

Abstract

Tungsten (W) nanoparticles were synthesised by using a novel low temperature molten salt technique. Na2WO4 and Al were used as starting materials, and NaCl, KCl, and NaF used to form the reaction media. Among the three salts, NaF showed the best accelerating effect in the W formation. When it was used alone, phase pure W could be produced after 4h at 850°C. On the other hand, when it was combined with the other two salts (forming a NaCl–KCl–NaF eutectic salt), phase pure W nanoparticles could be produced at as low as 650°C. As no water-insoluble by-product phases formed in the final samples, acid leaching which has to be used by many other techniques previously proposed, can be avoided. In addition, the by-product NaAlO2, happening to be the key intermediate product phase in the Bayer process, could be further used to prepare two important industrial materials Al2O3 and Na2CO3, adding more value to the molten salt technique developed with this work.